This invention relates to vertical furnaces as used in semiconductor manufacture in general and more particularly to the lift mechanism for moving the heater into and out of the furnace.
Various lifts and elevators as used in vertical furnaces use variations of vertical spiral drives for moving the lift or elevator. In U.S. Pat. No. 6,168,427 issued on Jan. 2,2001 and entitled xe2x80x9cApparatus for Guiding the Removal of a Processing Tube From a Semiconductor Furnacexe2x80x9d teaches a semiconductor wafer boat elevator including a boat support coupled by a lateral arm to a vertical spiral drive which moves the elevator up and down, beneath the furnace. This patent is assigned to a common assignee.
U.S. Pat. No. 6,171,453 issued on Jan. 9,2001 and entitled xe2x80x9cAlignment Mark Shielding Ring and Method of Usingxe2x80x9d shows a wafer pedestal elevator to move the wafers into and out of the processing chamber. The movement of the elevator is typically by a vertical spiral drive. This patent is assigned to a common assignee.
U.S. Pat. No. 6,095,806 issued on Aug. 1,2000 entitled xe2x80x9cSemiconductor Wafer Boat and Vertical Heat Treating Systemxe2x80x9d teaches the use of a ball screw to move a transfer base in a vertical direction. The transfer base is guided in the vertical direction by two guide rails. In addition, another ball screw is used to move an arm carrying the wafer boat. The arm moves into and out of a processing chamber that is sealed.
In most all of the various lift lead screw mechanism, the backlash tolerance in the lead screw give rise to positioning problems. Such positioning problems create wafer scrap and lead to a maintenance program that is frequently causing the lift to be off-line. In addition the starting torque of the lift mechanism is high and the actual running of the lift mechanism along its shaft is not as smooth as desired.
These and other operational problems are substantially reduced and even eliminated in the following vertical semiconductor furnace a heater lift lead screw having a multiple diameter shaft with a first tubular bearing surface at a first end. At the opposite end of the shaft is an elongated tubular surface.
A pillow block support receives the first tubular bearing surface of the shaft and supports the shaft for rotation. A motor is positioned axially in line with the pillow block support and receives the elongated tubular surface of the shaft. The motor provides the power to rotate the shaft either a clockwise or counterclockwise direction in the pillow block support.
The shaft has a threaded portion intermediate the first and second ends of the shaft. The threaded portion has a diameter that is larger than the diameter of the first bearing surface and the elongated tubular surface. A linear actuator member with an axially extended internal threaded portion is threadably mounted on the threaded portion of the shaft for transverse travel along the threaded portion under the control of the motor. A flange is mounted on the linear actuator in a position that is transverse to the axially extended threaded portion of the shaft. The flange supports a platform that carries furnace heater into and out of the furnace in the preferred embodiment.